1. Field of the Invention
The invention relates to location monitoring hardware and software systems. More specifically, the field of the invention is that of systems and methods for tracking and focusing imaging devices.
2. Description of the Related Art
One on the greatest challenges in photography, especially moving picture photography or videography, is that of managing the focus of the relevant imaging devices. At the most fundamental level, the depth of focus of the imaging device can be made as great as possible, thereby to allow all objects within the scene of interest to remain in focus. While this “deep focus” technique works well for panoramic outdoor scenes bathed in large amounts of light, the large f-numbers required for the necessary depth of focus demand massive amounts of light. As a result, this approach is not feasible for scenes with less light or “moody” scenes. Cinematographers also set great store by their ability to precisely manage the focus of scenes, as this has great impact on the actual “movie experience”. Maintaining a very large depth of focus is therefore not a method used extensively for general videography or cinematography. It is in the rest of the videography or cinematography, beyond “deep focus”, that the main challenge in focusing is to be found. Over the past few decades several methods have been developed to address this challenge. These fall mainly into two categories.
The first category comprises methods based on analyzing the image, or a part of it, on a continuous basis and to adjust the focus of the camera based on the change in focus or contrast in the image produced within the imaging device. There is a considerable range of implementations of this basic concept, some working more reliably than others. Most of these methods suffer from the difficulty of determining whether the imaging device is focused in front of or beyond the subject of interest. This results from the fact that either condition produces a decrease in contrast or a loss of focus. While some more sophisticated techniques tend to address this phenomenon to some degree, it remains a debilitating issue. As a result, automatic focus systems, more commonly known as “autofocus” systems, tend to “hunt” for focus. This can have hugely debilitating consequences for shooting scenes in which the subject is moving.
A considerable amount of data processing is associated with these focus-based autofocus systems. The availability of ever lower cost and higher speed processors makes the implementation of these systems ever more attractive, particularly in consumer photography and videography. However, even with these advances the slow hunt for focus by many autofocus systems remains a frustrating aspect of photography and videography.
A second category of focus methods is based on distance measurement. The most popular of these is the use of an ultrasonic rangefinder on the imaging device to determine the distance to the subject. This works well for subjects that are at very distinct distances and positions with respect to their surroundings, but these techniques struggle in environments where there is clutter. Fundamentally, the resolution of the technology is not adequate to the challenge of photographing or videographing a subject, say an actor, in a room full of objects, particularly of the subject or actor is moving through that environment. Given that the ultrasonic beam is not visible to the naked eye, there is considerable difficulty in directing and tracking it.
A need therefore remains for a reliable method of focusing imaging devices based on the position of the subject of interest within a scene or environment, particularly if the subject is moving through the scene or environment.